Respiratory Gas Monitors (=RGM) of the diverting type have a gas pump for drawing a flow of sample gas from the airway of the patient to the RGM. The sample gas is conducted from the sampling site to the RGM by a line with typically 2-3 meters length and internal diameter of about 1.2 mm. The mechanical motion needed for the pumping action is generated using an electrical motor or a solenoid mechanism in the pump. Gas pumps also contain valves actuated by pressure differences within the pump. Regardless of the type of the actuator and the valves, moving mechanical parts in the pump are subjected to stresses and wear, which limit the operating life of the pump. The relatively short operating life of the pump—typically in the order of 5000 hours—is often one of the main factors limiting the reliability of a RGM. When the pump in a RGM fails, the sample gas flow may stop completely or decrease to an unacceptable level. In many RGMs, the sample flow is measured and an alarm is given to the user when the flow is too low. The value of such alarm is quite limited, however, because monitoring of respiratory gases is no more possible after a pump failure. In some RGMs, low flow may remain undetected and lead to measurement errors that may compromise patient safety.
In the prior art, the gas pump in a RGM is running always when the RGM is switched on. Alternatively, unnecessary operation of the pump can be prevented by manually setting the RGM to a “Standby” mode, when gas monitoring is not needed. When a patient is again connected to the RGM, the user must manually switch the monitor from the Standby mode to the normal Operation mode. Often the RGM is kept running continuously for long periods of time even if the need for gas monitoring would be only very intermittent. The reason for this is that many RGMs need warm up time of several minutes, and most users want to avoid waiting for the warm-up by keeping their RGMs continuously on. It is common that the RGM is switched on in the morning or at the beginning of a work shift and turned off in the evening or at the end of the work shift. In some hospitals, the RGMs may even be switched on for 24 hours a day. A substantial part of the operating hours of the gas pump often consists of periods, when there is no need for respiratory gas monitoring. Even if the RGM could be manually switched to Standby mode, users tend to forget it, because they are busy with more important tasks, when disconnecting a patient from the RGM. If a gas pump is running for 12 hours a day, it typically fails about twice in three years, which means that it is one of the main factors limiting the “mean time between failures” of a RGM. The gas pump in a RGM is connected to both the pneumatics in the RGM and to the electronics circuitry. The replacement of a failed pump must be performed very skillfully in order to eliminate risks for new damages to the electronic circuits, such as those caused by electrostatic discharges and new faults in the pneumatics system, such as gas leakages. Thus, only a qualified service technician may change the pump. This means that the replacement is costly and it may take a substantial time to have the RGM repaired after a pump failure.